1. Field of the Invention
The present invention is generally related to the field of orthopedics, and, more particularly, to retractor instrumentation for total hip arthroplasty, and methods of using same.
2. Description of the Related Art
In the field of orthopedics, hip replacement is very common. Each year an estimated 300,000 people undergo hip replacement surgery. That number is expected to increase as the population continues to age, particularly within the United States. Most people have hip replacement surgery because of osteoarthritis, a degenerative joint disease. Basically, hip replacement surgery typically involves positioning a cup, having a plastic liner, in the pelvis, and positioning a stem down inside the femur. A ball on top of the stem is positioned within the cup in a ball-and-socket arrangement thereby allowing the hip to move normally.
Standard hip replacement surgery usually involves a relatively large 10–12″ incision, considerable pain, and an extended stay in the hospital, e.g., approximately 7 days. Additional recovery time may be required depending upon the particular patient and the circumstances of the surgeries. In some cases, efforts are being made to perform hip replacement surgery in a less invasive manner. Typically, such less invasive procedures, sometimes referred to as minimally invasive total hip arthroplasty, involve only a 3–4″ incision. Such minimally invasive procedures are typically more beneficial to the patient as the patient experiences significantly less pain and regains function of the hip much more quickly. More specifically, minimally invasive surgical techniques involve less cutting through muscles, less blood loss and often shorter hospital stays.
Although such minimally invasive hip replacement surgical techniques are more beneficial to the patient, they tend to be more difficult for a surgeon to perform due to the limited access to the surgical site by virtue of the smaller incision in the patient. When an incision is made in human skin, normally, because of the resilience of the tissue and skin, the incision will tend to remain closed. For a surgeon to perform an operation through the incision, it is necessary that the tissue at the edges of the incision be held back to give the surgeon room and access to perform the operation. Retractors are used for this purpose. In some cases, the retractors are held by assistants and comprise metal instruments having handle portions and hooked ends which can engage the edges of the incision. In other cases, by virtue of the design of the retractor, spaced separating members which engage the incision edges are held in spaced condition by spring or jack means or the like. The latter type of equipment is relatively complicated mechanically, but it may reduce the number of assistants involved as compared to the handheld retractors.
In some cases, prior art retractor methods were beneficial for part of the hip replacement surgery but not for all aspects of the surgery. For example, one illustrative retraction methodology involved use of two upstanding spaced-apart Charnley pins that were traditionally positioned superior to the acetabular and remained in an upright position. Typically, a chain was positioned between the two Charnley pins to assist with the retraction function. During a typical hip replacement procedure, the Charnley pins provided sufficient retraction such that the surgeon could readily access the pelvis area for purposes of installing the replacement acetabular cup. However, when the surgeon then attempted to install the stem in the patient's femur, it was often the case that the upstanding Charnley pins would interfere with part of that procedure. Thus, in some cases, one or more of the Charnley pins were removed, thereby reducing the retraction function of the pins. Moreover, given the tendency towards the minimally invasive hip replacement surgery, with its associated reduced incision length, prior art methodologies of retraction may not be readily adapted or employed in such minimally invasive procedures.
Another problem associated with total hip replacement surgery involves insuring that after the operation is completed the patient's leg is the appropriate length. Historically, problems have arisen with hip replacement surgery wherein the leg length of the patient after surgery is less than ideal, i.e., it is too short or too long relative to its pre-operative length. This may be due to, among other things, the improper positioning of the hip replacement components within the patient. Problems also arose in situations where it was desired to shorten or lengthen a patient's natural leg length during hip replacement surgery. That is, due to a variety of reasons, the surgeon was unable to obtain a desired or target length for the patient's leg after the hip replacement surgery is complete. Fundamentally, problems with achieving correct leg length involved difficulty in identifying and maintaining various reference points that would thereby allow the surgeon to confirm the correct positioning of the patient's leg with the hip replacement components installed in the patient.
The present invention is directed to various devices and methods for solving, or at least reducing the effects of, some or all of the aforementioned problems.